1. Field of the Invention
The present invention relates to a transformerless charger for charging a secondary battery placed in rechargeable electronic equipment such as a cordless phone or a mobile phone.
2. Description of the Related Art
Conventional chargers for charging secondary batteries placed within various kinds of electronic equipment for home appliances, such as cordless phones are constructed in order to facilitate charging operations, in such a manner that the relevant rechargeable electronic equipment can be charged simply by mounting the rechargeable electronic equipment on a mounting table on which a charging terminal is provided. If this kind of charger is provided with a transformer power supply circuit that prevents a human body from receiving an electric shock from the charging terminal, this may cause an increase in cost and weight. Moreover, since the transformer which requires a relatively large volume has to be incorporated into the charger, such construction causes the inconvenience of a charger which is designed to have limited usability.
In order to solve the aforementioned problem, a transformerless charger into which the transformer power supply circuit is incorporated has been suggested, which has made it possible to enhance the usability in designing the charger. However, since the charging terminal of the transformerless charger is continuously energized, it is necessary to prevent a human body from directly touching the charging terminal in order to secure safety.
However, if an area around the charging terminal is covered with some protective covering member, it is effective for the prevention of electric shocks, but it makes it difficult to clean the charging terminal. Particularly, in an environment containing a lot of dust or moisture, exogenous materials which make contact with the charging terminal cause chemical reactions, thereby bringing about a problem of shortening the life of the charging terminal.